Foot and mouth outbreak blamed on human action
An initial report by the UK Health and Safety Executive (HSE) into the source of the outbreak of foot and mouth disease has said there is a “strong probability” that the virus originated at either the Institute for Animal Health (IAH) or pharmaceutical manufacturer Merial Animal Health, both of which operate out of a site in Pirbright, close to the two outbreaks confirmed so far.
So far it has been confirmed that the strain of virus found at the outbreak farm was being worked on by both IAH and Merial during the period when infection was most likely to have occurred. This involved large scale production at the Merial site (10,000 litres) and a series of small-scale experiments (less than 10ml in each case) at the IAH site.
Further studies have been initiated, which are intended to provide additional molecular information on the virus types in use at both organisations, and results are expected within a week.
Investigations focused on biosecurity issues and whether or not there had been any lapses in control measures which could have led to a breach in biosecurity and whether these could be linked to the outbreak. This involved checking key biosecurity measures including engineering controls, management systems, working practices and a review of the record logs.
The HSE found no evidence of any working practices or incidents such as laboratory spillages or leakages from plant or equipment that could have led to a release of the FMDV strain within the contained working environment at either organisation. It confirmed that all air being discharged to atmosphere from the contained working environments is first passed through a minimum of two HEPA air filters, that there is continuous monitoring of the pressures of the ventilation systems of the facility and that the HEPA filters are routinely integrity tested in line with regulatory requirements.
Examination of local wind conditions indicates that there was only a very limited period during which the wind could have acted as a transmission link. This would have had to coincide with a release of virus through the ventilation system, but the HSE found no evidence of such a release. It has therefore virtually ruled out an airborne release of the virus from the IAH or the Merial sites.
Waterborne release remains a possibility, but preliminary investigations into the possibility of whether surface water from flooding from the site could have reached and contaminated the affected farm have indicated that this was negligible due to the distance, topography and direction of flow.
Two separate effluent treatment systems exist on Pirbright site: one that services the animal isolation unit at the IAH and one that services both the remainder of the IAH site together with the Merial site. The effluent treatment system servicing the IAH animal isolation unit employs a thermal inactivation process and appears to have been operating satisfactorily during the likely infection period.
The effluent treatment system servicing the remainder of the IAH site together with the Merial site employs a chemical inactivation process. While control measures are in place at both premises to require chemical treatment of liquid effluent before it enters the system, a number of biosecurity issues have arisen that are subject to ongoing investigation, according to the HSE.
These include:
- the integrity of the system and all associated pipework;
- the potential for the virus to have entered this system during the specified time period;
- whether heavy rain and flooding during the period may have overwhelmed this system;
- whether any contaminated material could have been transferred between the IAH and Merial sites and the first affected farm.
For virus to escape from the effluent pipe, a failure in the intermediate inactivation process either at the Merial or IAH site would have had to occur and this would have had to coincide with the flooding.
The HSE therefore considers that release by human movement must be considered a real possibility. There are various potential routes for accidental or deliberate transfer of material from the site, it says, and after investigating site management systems and records and having spoken to a number of employees it is urgently pursuing lines of inquiry in these areas.
Merial has conducted "intensive internal investigations" and had "complete confidence" in its processes and procedures. It had not found any evidence the virus could have been transported out of the centre by humans, it said. The company added that it did not release water from the site.